Intact peripheral chemoreflex regulation of sympathetic vasomotor tone in breath hold divers after detraining period

We tested the hypothesis that peripheral chemoreceptor function in response to hypoxia is normal in breath‐hold divers (BHD) after detraining period. We compared ventilatory, sympathetic (MSNA), heart rate and blood pressure responses to isocapnic hypoxia in 11 BHD and 11 control subjects. The study was carried out at least one month after all divers finished most intensive apnea training. After baseline period for instrumentation, subjects breathed isocapnic hypoxic mixture to reduce arterial saturation to 0.8. During hypoxia burst frequency (MSNA f ) and total activity (MSNA t , au/min) increased similarly in both groups (27% and 60% in BHD and 30% and 66% in controls), respectively. Increased MSNA f and MSNA t returned to baseline after 20 min after termination of hypoxia. Hypoxia‐induced stimulation of minute ventilation was similar in both groups. Cardiac output was increased during hypoxia and since mean blood pressure was unchanged, total peripheral resistance was similarly reduced in both groups. We conclude that elite divers at least 1 month after the end of intensive training/competition period have normal peripheral chemosensitivity without any ventilatory, hemodynamic and autonomic differences from those observed in control subjects. This study was supported by the Croatian Ministry of Science, Education and Sports.